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Basic Info

Model NO.: BOSJ-T

Application: Audi

Brand: MITSUBISHI

Making Machine: 5 Axis

Trademark: BOSJ

Specification: BOSJ-T

Origin: Jiangsu

Product Description

TurbineEnergy provided for the turbine work is converted from the enthalpy and kinetic energy of the gas&period; The turbine housings direct the gas flow through the turbine as it spins at up to 250&comma;000 rpm&period; The

size and shape can dictate some performance characteristics of the overall turbocharger&period; Often the same basic turbocharger assembly is available from the manufacturer with multiple housing choices

for the turbine&comma; and sometimes the compressor cover as well&period; This lets the balance between performance&comma; response&comma; and efficiency be tailored to the application&period;

The turbine and impeller wheel sizes also dictate the amount of air or exhaust that can be flowed through the system&comma; and the relative efficiency at which they operate&period; In general&comma; the larger the

turbine wheel and compressor wheel the larger the flow capacity&period; Measurements and shapes can vary&comma; as well as curvature and number of blades on the wheels&period;

On the left&comma; the brass oil drain connection&period; On the right are the braided oil supply line and water coolant line connections&period;

Compressor impeller side with the cover removed&period;

Turbine side housing removed&period;A turbocharger's performance is closely tied to its size&period; Large turbochargers take more heat and pressure to spin the turbine&comma; creating lag at low speed&period; Small turbochargers spin quickly&comma; but may

not have the same performance at high acceleration&period; To efficiently combine the benefits of large and small wheels&comma; advanced schemes are used such as twin-turbochargers&comma; twin-scroll turbochargers&comma;

or variable-geometry turbochargers&period;

Twin-turbo

Twin-turbo or bi-turbo designs have two separate turbochargers operating in either a sequence or in parallel&period; In a parallel configuration&comma; both turbochargers are fed one-half of the engine's

exhaust&period; In a sequential setup one turbocharger runs at low speeds and the second turns on at a predetermined engine speed or load&period; Sequential turbochargers further reduce turbo lag&comma; but require an

intricate set of pipes to properly feed both turbochargers&period;

Two-stage variable twin-turbos employ a small turbocharger at low speeds and a large one at higher speeds&period; They are connected in a series so that boost pressure from one turbocharger is multiplied

by another&comma; hence the name "2-stage&period;" The distribution of exhaust gas is continuously variable&comma; so the transition from using the small turbocharger to the large one can be done incrementally&period; Twin

turbochargers are primarily used in Diesel engines&period; For example&comma; in Opel bi-turbo Diesel&comma; only the smaller turbocharger works at low speed&comma; providing high torque at 1&comma;500-1&comma;700 rpm&period; Both

turbochargers operate together in mid range&comma; with the larger one pre-compressing the air&comma; which the smaller one further compresses&period; A bypass valve regulates the exhaust flow to each turbocharger&period;

At higher speed &lpar;2&comma;500 to 3&comma;000 RPM&rpar; only the larger turbocharger runs&period;

Smaller turbochargers have less turbo lag than larger ones&comma; so often two small turbochargers are used instead of one large one&period; This configuration is popular in engines over 2&comma;500 CCs and in V-

shape or boxer engines&period;

Twin-scroll

Twin-scroll or divided turbochargers have two exhaust gas inlets and two nozzles&comma; a smaller sharper angled one for quick response and a larger less angled one for peak performance&period;

With high-performance camshaft timing&comma; exhaust valves in different cylinders can be open at the same time&comma; overlapping at the end of the power stroke in one cylinder and the end of exhaust stroke

in another&period; In twin-scroll designs&comma; the exhaust manifold physically separates the channels for cylinders that can interfere with each other&comma; so that the pulsating exhaust gasses flow through

separate spirals &lpar;scrolls&rpar;&period; With common firing order 1-3-4-2&comma; two scrolls of unequal length pair cylinders 1-4 and 3-2&period; This lets the engine efficiently use exhaust scavenging techniques&comma; which

Variable-geometryVariable-geometry or variable-nozzle turbochargers use moveable vanes to adjust the air-flow to the turbine&comma; imitating a turbocharger of the optimal size throughout the power curve&period; The vanes are

placed just in front of the turbine like a set of slightly overlapping walls&period; Their angle is adjusted by an actuator to block or increase air flow to the turbine&period; This variability maintains a

comparable exhaust velocity and back pressure throughout the engine's rev range&period; The result is that the turbocharger improves fuel efficiency without a noticeable level of turbocharger lag&period;

CompressorThe compressor increases the mass of intake air entering the combustion chamber&period; The compressor is made up of an impeller&comma; a diffuser and a volute housing&period;Main article&colon; Centrifugal compressorThe operating range of a compressor is described by the "compressor map"&period;

Illustration of inter-cooler location&period;When the pressure of the engine's intake air is increased&comma; its temperature also increases&period; In addition&comma; heat soak from the hot exhaust gases spinning the turbine may also heat the intake air&period; The warmer the intake air&comma; the less dense&comma; and the less oxygen available for the combustion event&comma; which reduces volumetric efficiency&period; Not only does excessive intake-air temperature reduce efficiency&comma; it also leads to engine knock&comma; or detonation&comma; which is destructive to engines&period;

Turbocharger units often make use of an intercooler &lpar;also known as a charge air cooler&rpar;&comma; to cool down the intake air&period; Intercoolers are often&lsqb;when&quest;&rbrack; tested for leaks during routine servicing&comma; particularly in trucks where a leaking intercooler can result in a 20&percnt; reduction in fuel economy&period;&lsqb;citation needed&rbrack;

&lpar;Note that intercooler is the proper term for the air cooler between successive stages of boost&comma; whereas charge air cooler is the proper term for the air cooler between the boost stage&lpar;s&rpar; and the appliance that consumes the boosted air&period;&rpar;

Water injection

An alternative to intercooling is injecting water into the intake air to reduce the temperature&period; This method has been used in automotive and aircraft applications&period;

Fuel-air mixture ratio

In addition to the use of intercoolers&comma; it is common practice to add extra fuel to the intake air &lpar;known as "running an engine rich"&rpar; for the sole purpose of cooling&period; The amount of extra fuel varies&comma; but typically reduces the air-fuel ratio to between 11 and 13&comma; instead of the stoichiometric 14&period;7 &lpar;in petrol engines&rpar;&period; The extra fuel is not burned &lpar;as there is insufficient oxygen to complete the chemical reaction&rpar;&comma; instead it undergoes a phase change from atomized &lpar;liquid&rpar; to gas&period; This phase change absorbs heat&comma; and the added mass of the extra fuel reduces the average thermal energy of the charge and exhaust gas&period; Even when a catalytic converter is used&comma; the practice of running an engine rich increases exhaust emissions

WastegateMany turbochargers use a basic wastegate&comma; which allows smaller turbochargers to reduce turbocharger lag&period; A wastegate regulates the exhaust gas flow that enters the exhaust-side driving turbine and therefore the air intake into the manifold and the degree of boosting&period; It can be controlled by a boost pressure assisted&comma; generally vacuum hose attachment point diaphragm &lpar;for vacuum and positive pressure to return commonly oil contaminated waste to the emissions system&rpar; to force the spring loaded diaphragm to stay closed until the overboost point is sensed by the ecu or a solenoid operated by the engine's electronic control unit or a boost controller&comma; but most production vehicles use a single vacuum hose attachment point spring loaded diaphragm that can alone be pushed open&comma; thus limiting overboost ability due to exhaust gas pressure forcing open the wastegate&period;

Anti-surge&sol;dump&sol;blow off valves

Turbocharged engines operating at wide open throttle and high rpm require a large volume of air to flow between the turbocharger and the inlet of the engine&period; When the throttle is closed&comma; compressed air flows to the throttle valve without an exit &lpar;i&period;e&period;&comma; the air has nowhere to go&rpar;&period;

In this situation&comma; the surge can raise the pressure of the air to a level that can cause damage&period; This is because if the pressure rises high enough&comma; a compressor stall occurs-stored pressurized air decompresses backward across the impeller and out the inlet&period; The reverse flow back across the turbocharger makes the turbine shaft reduce in speed more quickly than it would naturally&comma; possibly damaging the turbocharger&period;

To prevent this from happening&comma; a valve is fitted between the turbocharger and inlet&comma; which vents off the excess air pressure&period; These are known as an anti-surge&comma; diverter&comma; bypass&comma; turbo-relief valve&comma; blow-off valve &lpar;BOV&rpar;&comma; or dump valve&period; It is a pressure relief valve&comma; and is normally operated by the vacuum in the intake manifold&period;

The primary use of this valve is to maintain the spinning of the turbocharger at a high speed&period; The air is usually recycled back into the turbocharger inlet &lpar;diverter or bypass valves&rpar;&comma; but can also be vented to the atmosphere &lpar;blow off valve&rpar;&period; Recycling back into the turbocharger inlet is required on an engine that uses a mass-airflow fuel injection system&comma; because dumping the excessive air overboard downstream of the mass airflow sensor causes an excessively rich fuel mixture-because the mass-airflow sensor has already accounted for the extra air that is no longer being used&period; Valves that recycle the air also shorten the time needed to re-spool the turbocharger after sudden engine deceleration&comma; since load on the turbocharger when the valve is active is much lower than if the air charge vents to atmosphere&period;